Not into doing stuff on your own, huh? Oh well...more fun for me. Before I begin though, I'm assuming that you mean the secret aeons because the other aeons (Valefor, Ifrit, Ixion, Shiva, Bahamut) you recieve as the game progresses.

Yojimbo

In the Calm Lands, circle past the right side of the bridge leading to Mt. Gagazet, and descend into the gorge below. To the left of the Save Sphere is the Cavern of the Stolen Fayth. Proceed through the cave until you encounter the spirit of a dead summoner. The summoner will call Yojimbo. This aeon has high physical defense but low magic defense, so hit him as often as possible with spells such as Firaga. Afterward, you can use the teleport pad there to travel to hidden chambers containing a Flexible Arm, an MP Sphere, and two X-Potions. Next, travel to the Chamber of the Fayth and speak to Yojimbo to negotiate a fee for his services. He will offer his lowest initial asking price if you choose the option "To defeat the most powerful of enemies." For your first bid, offer half of his asking price plus 1 Gil. So, if he asks for 250,000 Gil, offer 125,001 Gil. After his next offer, raise your bid by 1 Gil. By the time he proposes 205,000 Gil, he will generally accept offers below 200,000 Gil, though not much lower. If at any point you offer him at least triple his asking price, he will give you two Teleport Spheres in addition to his services.

Anima

First find the hidden location Baaj Temple with the airship (X Coordinate = 11-16, Y Coordinate = 57-63). Run up the familiar path and dive into the water. Now you must defeat Geosgaeno. After you beat him you can swim towards the underwater temple entrance. Enter the Chamber of the Fayth, where you'll find four Mega Phoenix items and a Megalixir. Approach the six statues on either side. There is one hidden item in each of Spira's six Cloisters of Trials. You should have found five of these items at this point, and five of the statues in this room will activate as a result (If you didn't find them, go back and get them now). Now you just need to get the last item from Zanarkand Dome. Fly to Zanarkand and enter the dome. Once there, a new puzzle solution is displayed on the screen. Step on the three white squares in the first room and the four in the larger chamber. This opens a panel in the first room revealing a Destruction Sphere. Place the Destruction Sphere into the slot to the right of the monitor in the large chamber, and the screen will explode. Coolect the Magistral Rod, and return to Baaj Temple. The six statues will now resonate with the items you have collected, allowing you to enter the Chamber of the Fayth. Now Anima is yours.

The Magus Sisters

To get the Magus Sisters, capture all of the required types of fiends on Mt. Gagazet and return to the monster arena owner in the Calm Lands. As a reward he gives you the Blossom Crown. You must also possess all of the other aeons, including Yojimbo and Anima. Next, go to Remien Temple in the Calm Lands. After you defeat Spathi, Belgemine will give you the Flower Scepter. After defeating all of the aeons at Remien Temple, use the Blossom Crown and Flower Scepter on the door in the back to unseal it and acquire the Magus Sisters.

So there you have it, all three of the secret aeons and how to get your hands on them. Have fun completing all the tasks to get them!

-DragoonMaster

On the airship enter YUEVONISGAY to unlock all aeaons.